The subject of the invention is a new catalytic composition and its use in oligomerizing, particularly dimerizing and trimerizing, monoolefins. More specifically, it concerns combinations obtained by placing at least one divalent nickel compound into contact with at least one hydrocarbylaluminum halide and at least one apoxy compound (also described as oxirane), in any order.
It is well known to prepare catalysts for dimerizing or codimerizing monoolefins, such as ethylene, propylene or n-butenes. Such catalysts may e.g. result from: interaction between halides of .pi.-allyl nickel phosphine and Lewis acids (FR-B-1 410 430), interaction between halides of nickel phosphine and Lewis acids (U.S. Pat. No. 3,485,881) or interaction between certain nickel carboxylates and hydrocarbylaluminum halides (U.S. Pat. No. 3,321,546). Other catalysts use zerovalent nickel compounds, though these are impractical because of their instability and high cost. It is generally preferable to use nickel compounds which are soluble in hydrocarbon materials.
Industrial application of the catalytic compositions described above to olefin cuts such as those emanating from petrochemical processes, such as catalytic or steam cracking, is encumbered by difficulties, particularly in connection with the impurities contained in the cuts.
These difficulties have been partly overcome by using improved catalytic formulations incorporating a divalent nickel compound, a hydrocarbylaluminum halide and a compound of the nature of a Bronsted acid (U.S. Pat. No. 4,283,305), or a combined compound of nickel in association with an alkylaluminum compound (U.S. Pat. Nos. 4,316,851, 4,366,087 and 4,398,049). These improved catalytic formulations usually include a halocarboxylic acid or the corresponding anion.